What it means, Stove, is that you will never survive a ninja attack.
But more seriously, I'm also a fan of the theory that the more you want/expect something to be there, the more likely you are to see it- whether or not it's really there.
Is that something like projected psychology?
It's related to the way the brain works; you need to remember that the amount of information coming in through your 5 senses is far too much for the brain to have any hope of processing all of it. So the brain cheats, it only actually processes the important bits, and then it actually
makes up the rest. 99.9% of the time it gets it right, because the brain is really good at making stuff up, sometimes it gets it wrong, and that leads to things like seeing faces out of the corner of your eyes, or thinking you heard something.
Of course, when it all goes wrong, you have hallucinations.
The only real reproducable example of this is the blind spot, an area of your vision that the eye cannot actually see because the retina gets in the way, your brain is constantly making up the contents of the blind spot, and if you know where it is and how to use it, you can have great fun with it. I used to amuse myself in long classes by using it to erase my teacher's head, as the brain would look at the 'border' of the blind spot, determine that the border was mostly the white space of the whiteboard, and so fill the blind spot with white space, erasing the teacher's head.